FIR: rename AMBIGUITY to OVERLOAD_RESOLUTION_AMBIGUITY to match FE 1.0

compiler/testData/diagnostics/tests/inference/cannotCompleteResolveAmbiguity.fir.kt

@@ -5,5 +5,5 @@ fun <T> g(i: Int, a: Any): List<T> {throw Exception()}
 fun <T> g(a: Any, i: Int): Collection<T> {throw Exception()}
 
 fun <T> test() {
-    val c: List<T> = <!AMBIGUITY!>g<!>(1, 1)
+    val c: List<T> = <!OVERLOAD_RESOLUTION_AMBIGUITY!>g<!>(1, 1)
 }